Valve deactivation device

Abstract

A valve deactivation device for a rocker arm assembly having a cam arm and a valve arm. A return spring biases a lock pin toward an activated position to allow the cam arm and the valve arm to rotate together. The lock pin can be translated against the biasing force of the return spring to decouple the cam arm and valve arm for relative rotation.

Description

TECHNICAL FIELD

The present invention relates generally to valve trains for internal combustion engines. More particularly, the present invention relates to a valve deactivation device for use in a valve train.

BACKGROUND OF THE INVENTION

Multi-cylinder internal combustion engines include a valve train having intake and exhaust valves disposed in the cylinder head above each combustion cylinder. The intake and exhaust valves connect intake and exhaust ports with each combustion cylinder. The intake and exhaust valves are generally poppet-type valves having a generally mushroom-shaped head and an elongated cylindrical stem extending from the valve head. A spring biases the valve head in a fully closed position against a valve seat in the cylinder head. Historically, engine valves were actuated from the fully closed position to a fully open position by an underhead camshaft, pushrod, and rocker arm assembly. Hydraulic lifters, which utilize pressurized hydraulic fluid to actuate a piston to reciprocate the valve, were added as a buffer between the motion of the rocker arm and the valve stem and as a means for adjusting valve lash. In later developments, overhead camshafts eliminated the pushrod and, occasionally, the rocker arm for a more direct actuation of the valves.

Reduction of fuel consumption and improved emissions, especially for passenger cars, have been important considerations for internal combustion engine design. One engine design change for reducing fuel consumption and improving emissions has been a shutdown of individual cylinders during engine operation, especially during partial load. A cylinder shutdown increases intake manifold pressure thereby allowing the remaining cylinders to operate at increased average pressure and thus have a reduced specific consumption. For cylinder shutdown, it is not only necessary to provide for an interruption of the fuel supply, it is furthermore expedient to interrupt the load flow through the respective cylinder by shutting down the one or more valves, especially the intake valve of the respective cylinder.

Valve deactivation devices have been employed to desirably shut down valves in an operating engine. When valves are deactivated, friction losses in the valve train are reduced. Many prior art valve deactivation devices undesirably include numerous components that make the devices costly to produce and assemble. Other prior art devices operate by decoupling components of rocker arms that do not necessarily realign in order to recouple and reactivate the rocker arm. What is needed, is a valve deactivation device that permits a rocker arm assembly to deactivate using fewer moving parts than prior art assemblies.

SUMMARY OF THE INVENTION

The present invention is directed to a rocker arm assembly having a valve deactivation device for a valve train. Each rocker arm assembly of the valve train may be switchable between an activated condition and a deactivated condition. In one embodiment, the rocker arm assembly includes a valve arm, a cam arm that is rotatably coupled to the valve arm, and a valve deactivation device. The valve deactivation device is coupled to the cam arm. The valve deactivation device includes a lock pin that selectively cooperates with a surface of the valve arm to switch the rocker arm assembly to the activated condition. The lock pin is moveable between a deactivated position and an activated position, the activated position corresponding to the activated condition, and the deactivated position corresponding to the deactivated condition.

In another embodiment of the invention, a rocker arm assembly includes a valve arm, a cam arm, and a valve deactivation device. The cam arm is rotatably coupled to the valve arm. The valve arm and the cam arm are rotatable generally about a common axis. The common axis is defined by a rocker shaft. At least a portion of the valve arm and at least a portion of the cam arm are concentrically positioned about the common axis. The valve deactivation device is coupled to the rocker arm assembly to switch the rocker arm assembly between an activated condition and a deactivated condition.

In a further embodiment, a valve deactivation device for a rocker arm assembly includes a hydraulically operated lock pin coupled to the rocker arm assembly and a return spring biasing the lock pin in the activated position. The lock pin selectively engages a surface of the rocker arm assembly to switch the rocker arm assembly to an activated condition. The lock pin is moveable between a deactivated position and an activated position, the activated position corresponding to the activated condition, and the deactivated position corresponding to a deactivated condition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a valve train assembly.

FIG. 2 is a perspective view of a rocker arm assembly that includes a valve deactivation device in accordance with the present invention.

FIG. 3 is a rear perspective view of the rocker arm assembly of FIG. 2.

FIG. 4 is a perspective view of the valve deactivation device of FIG. 2, illustrating some portions in phantom.

FIG. 5 is a sectional view taken along line 5-5 of FIG. 2.

FIG. 6 is a sectional view similar to FIG. 5, illustrating the valve deactivation device in accordance with the present invention in a deactivated condition.

DESCRIPTION OF A PREFERRED EMBODIMENT

With reference to FIG. 1, a valve train assembly 20 is shown. Valve train assembly 20 includes a pair of rocker shafts 22, having an axis A-A, with attachment bolts 24 interposed therethrough and a plurality of rocker arm assemblies 30 rotatably coupled thereto along the axial length of rocker shafts 22. Attachment bolts 24 secure rocker shafts 22 to a head assembly (not shown).

Referring now to FIGS. 2-4, rocker arm assembly 30 includes a cam arm 32 having a valve arm 34 journaled therein, a cam arm retaining clip 36, a spring retaining clip 38, and an arm spring 40. Cam arm 32 includes a generally tubular cam body portion 50 having an arm portion 52 (FIG. 2) and a deactivation device, or deactivation portion, 54 extending therefrom. Arm portion 52 includes a cam spring pin 56 extending therefrom, a bifurcated end 58 (FIG. 2) having a roller 60 (FIG. 2) rotatably coupled thereto via a roller pin 62 (FIG. 2). Roller pin 62 interposed through both the bifurcated end 58 and the roller 60.

Valve arm 34 includes a generally tubular valve body portion 64 having an arm portion 66 extending therefrom. Arm portion 66 includes a proximal end 68 attached to valve body portion 64 and a distal end 70 having a valve contacting portion 72 attached thereto. Arm portion 66 further includes a valve spring pin 74 extending therefrom, a lock pin aperture 76 (FIGS. 5 and 6) formed therein, and a lock pin sliding surface 78 (FIG. 3). Cam body portion 50 is a hollow elongated cylinder that includes a first annular end 80, a second annular end 82, a generally cylindrical cam arm inner surface 84 (FIG. 3), and a generally cylindrical cam arm outer surface 86.

With specific reference to FIGS. 5 and 6, deactivation portion 54 includes a generally tubular body 88, which, in one embodiment, is a hollow elongated cylinder having an end 90, attached to the cam body portion 50. In one embodiment, a lock pin 92 is at least partially housed within body 88 and positioned so as to be in engagement with a return spring 94. Deactivation portion 54 may also include a return spring 94, and a cap 96 secured to end 90. Cap 96 closes off body 88 and provides a surface for return spring 94 to act against. Alternately, end 90 may be provided with mounting shoulders for return spring 94 to act against, thereby eliminating the need for cap 96.

Referring again to FIGS. 2-4, the valve body portion 64 is a hollow elongated cylinder that includes a first annular end 100 (FIG. 3), a second annular end 102 (FIG. 2), a generally cylindrical valve arm inside surface 104, and a generally cylindrical valve arm outside surface 106. Valve body portion 64 also includes a pair of annular retaining grooves 108 formed in valve arm outside surface 106, adjacent the first annular end 100 and the second annular end 102, respectively.

Valve contacting portion 72 includes a housing 110 that retains a lash adjuster 114. Lash adjuster 114 contacts the stem of a valve (not shown) for operation thereof.

Arm spring 40 is mounted on second annular end 102 of valve body portion 64. In one embodiment, arm spring 40 includes a curved body 118 that defines an arcuate section. Curved body 118 has an open section 120, flanked by a valve pin end 122 and a cam pin end 124.

Lock pin 92 is illustrated in FIGS. 5 and 6 to include a generally cylindrical plunger portion 130 having a distal end 132 and a proximal end 134 integrally connected to a generally cylindrical piston portion 136. Lock pin aperture 76 includes a cylindrical pin surface 140 formed inside arm portion 66. Tubular body 88 includes a generally cylindrical piston surface 146 that slideably engages piston portion 136, a generally cylindrical pin outlet surface 148, and an oil inlet channel (not shown) that intersects the piston surface 146 defining an oil port 152. Collectively, plunger portion 130, piston surface 146 and piston portion 136 form a hydraulic cavity 160, as discussed below. The clearances between cylindrical piston surface 146 and cylindrical piston portion 136, and between cylindrical plunger portion 130 and pin outlet surface 148 are sufficiently small so as to allow pressure to build within hydraulic cavity 160 when pressurized oil is supplied through oil port 152 to hydraulic cavity 160.

As best seen in FIGS. 2 and 3, valve body portion 64 of valve arm 34 is interposed through cam body portion 50 of cam arm 32 with the first annular end 100 and the second annular end 102 protruding therefrom. Thus coupled, cam arm 32 and valve arm 34 are journaled for relative rotation therebetween about axis A-A. Arm spring 40 is superposed around second annular end 102. Valve pin end 122 of arm spring 40 is coupled to valve spring pin 74 and cam pin end 124 is coupled to cam spring pin 56. Arm spring 40 selectively biases cam spring pin 56 away from valve spring pin 74. Preferably, arm spring 40 is a partial coil spring with at least a portion thereof curved about axis A-A. Also preferably, arm spring 40 extends less than 360° about axis A-A. The cam arm retaining clip 36 is inserted into a retaining groove 108 to limit relative axial movement between valve arm 34 and cam arm 32. The spring retaining clip 38 is inserted into retaining groove 108 to retain arm spring 40 on valve body portion 64.

Referring again to FIGS. 5 and 6, lock pin 92 is positioned within tubular body 88 and in alignment with lock pin aperture 76. Lock pin 92 is moveable between an activated position (FIG. 5) and a deactivated position (FIG. 6). In FIG. 5, at least the distal end 132 of lock pin 92 is circumscribed by cylindrical pin surface 140 of lock pin aperture 76. In FIG. 6, return spring 94 is compressed between lock pin 92 and cap 96 by a force exerted by the pressure of oil contained within hydraulic cavity 160, as discussed below.

In operation, lock pin 92 is in the activated position of FIG. 5 thereby releasably coupling valve arm 34 and cam arm 32 for relative rotation. Cam arm retaining clip 36 prevents relative translation between valve arm 34 and cam arm 32 along axis A-A. As a camshaft (not shown) rotates and urges against roller 60 to rotate rocker arm assembly 30 about axis A-A, valve arm 34 rotates with cam arm 32 to operate a valve (not shown).

To deactivate rocker arm assembly 30 from the activated condition, pressurized oil is introduced into hydraulic cavity 160, thereby urging lock pin 92 toward cap 96, against the biasing force of return spring 94. When the lock pin 92 has moved out of engagement with lock pin aperture 76, valve arm 34 is free to rotate relative cam arm 32, thereby placing rocker arm assembly 30 in a deactivated condition. As the camshaft rotates further, urging roller 60, cam arm 32 rotates about axis A-A and valve arm 34 does not rotate. Since valve arm 34 does not rotate, the valve is not operated, and is effectively shut down. With relative rotation of cam arm 32 and valve arm 34, arm spring 40 is deflected, thereby storing energy and inducing a relative torsion between valve arm 34 and cam arm 32. This torsion urges roller 60 to generally stay in contact with the camshaft.

To activate rocker arm assembly 30 from the deactivated condition, pressurized oil is released from hydraulic cavity 160, thereby allowing return spring 94 to urge lock pin 92 toward valve arm 34. Depending upon the relative angular positions of valve arm 34 and cam arm 32, distal end 132 of lock pin 92 will contact either lock pin aperture 76, or lock pin sliding surface 78. When lock pin 92 contacts lock pin sliding surface 78, valve arm 34 will not rotate and arm spring 40 urges cam arm 32 to rotate as the camshaft rotates. As cam arm 32 rotates and valve arm 34 does not rotate, lock pin 92, in contact with lock pin sliding surface 78, follows a generally circular arc about axis A-A. As the camshaft rotates further, lock pin 92 will align with and engage lock pin aperture 76, thereby placing rocker arm assembly 30 in an activated condition. Thus, lock pin 92 is selectively guided into engagement with said cylindrical pin surface 140 of lock pin aperture 76 by the relative rotation of cam arm 32 and valve arm 34.

Preferably, the flow of oil into hydraulic cavity 160 is controlled by an electronic solenoid valve (not shown), although other conventional means may be utilized. Also preferably, oil flows through the solenoid valve, then through a channel (not shown) in the head, into the rocker shaft 22, through the valve arm 34, into the cam arm 32, through oil inlet channel, past oil port 152, and into the hydraulic cavity 160.

Lock pin 92 and lock pin aperture 76 may be cooperatively tapered such that the diameter of distal end 132 is smaller than the diameter of proximal end 134. With such a taper, lock pin 92 and lock pin aperture 76 will couple in a closer fitting arrangement, thereby reducing any slight relative rotation between cam arm 32 and valve arm 34. While the deactivation portion 54 has been described as attached to valve arm 34, it would be appreciated that deactivation device could be attached to cam arm 32 or other portions of valve train assembly 20 to accomplish the same purpose. While many components of valve train assembly are described as tubular or cylindrical, it is understood that at least some of these components and their complementary shaped components can be formed in shapes other than circular to perform at least a similar function.

It is to be understood that the above description is intended to be illustrative and not limiting. Many embodiments will be apparent to those of skill in the art upon reading the above description. Therefore, the scope of the invention should be determined, not with reference to the above description, but instead with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

1. A rocker arm assembly having a valve deactivation device, wherein the rocker arm assembly is selectively switchable between an activated condition and a deactivated condition, the rocker arm assembly comprising: a valve arm; a cam arm rotatably coupled to said valve arm; and a valve deactivation device coupled to said cam arm, said valve deactivation device having a lock pin that selectively cooperates with a surface of said valve arm, wherein said lock pin is moveable between a deactivated position and an activated position, said activated position corresponding to said activated condition, and said deactivated position corresponding to said deactivated condition.

2. The rocker arm assembly of claim 1, further comprising an arm spring selectively coupled to said valve arm and said cam arm, wherein said arm spring opposingly biases said valve arm and said cam arm thereby inducing a relative torsion therebetween.

3. The rocker arm assembly of claim 2, wherein said arm spring includes an arcuate section, wherein said arcuate section extends less than 360° around an axis of said arcuate section.

4. The rocker arm assembly of claim 1, wherein a portion of said valve arm is interposed within at least a portion of said cam arm.

5. The rocker arm assembly of claim 1, further comprising a return spring biasing said lock pin in said activated position.

6. The rocker arm assembly of claim 1, wherein said valve arm and said cam arm are rotatable generally about a common axis, said common axis being defined by a rocker shaft.

7. The rocker arm assembly of claim 1, wherein at least a portion of said valve arm and at least a portion of said cam arm are concentrically positioned about a common axis.

8. The assembly of claim 7, wherein an axis of said locking pin selectively follows a generally circular arc about said common axis.

9. The rocker arm assembly of claim 1, wherein said cam arm includes a roller follower.

10. The rocker arm assembly of claim 1, wherein said lock pin is selectively guided into engagement with said surface of said valve arm by relative rotation of said cam arm and said valve arm.

11. The rocker arm assembly of claim 1, further comprising a lash adjuster coupled to said valve arm.

12. A rocker arm assembly having a valve deactivation device, wherein the rocker arm assembly is switchable between an activated condition and a deactivated condition, the rocker arm assembly comprising: a valve arm; a cam arm rotatably coupled to said valve arm, wherein said valve arm and said cam arm are rotatable generally about a common axis, said common axis being defined by a rocker shaft, and wherein at least a portion of said valve arm and at least a portion of said cam arm are concentrically positioned about said common axis; and a valve deactivation device coupled to said rocker arm assembly.

13. The rocker arm assembly of claim 12, further comprising an arm spring selectively coupled to said valve arm and said cam arm, wherein said arm spring biases said valve arm and said cam arm for counter-rotation.

14. The rocker arm assembly of claim 13, wherein said arm spring includes an arcuate section, wherein said arcuate section extends less than 360° around an axis of said arcuate section.

15. The assembly of claim 12, wherein said cam arm includes a roller follower.

16. The assembly of claim 12, further comprising a lash adjuster.

17. The assembly of claim 12, wherein said valve deactivation device is hydraulically operated.

18. The assembly of claim 17, wherein said valve deactivation device is electronically controlled.

19. A valve deactivation device for a rocker arm assembly that is selectively switchable between an activated condition and a deactivated condition, the valve deactivation device comprising: a hydraulically operated lock pin coupled to a rocker arm assembly, wherein said lock pin selectively engages a surface of said rocker arm assembly to switch said rocker arm assembly to the activated condition, wherein said lock pin is moveable between a deactivated position and an activated position, said activated position corresponding to the activated condition, and said deactivated position corresponding to the deactivated condition; and a return spring biasing said lock pin in one of said deactivated position and said activated position.

20. The valve deactivation device of claim 19 wherein said valve deactivation device is electronically controlled.

21. The valve deactivation device of claim 19 further comprising a hydraulic cavity, wherein a pressurized fluid supplied to said hydraulic cavity urges said lock pin toward one of said deactivated position and said activated position.

22. The valve deactivation device of claim 21 wherein said lock pin is at least partially positioned within said hydraulic cavity.